Centrifugal impact milling machine



March 15, 1960 F. s. SMITH 2,928,616

CENTRIFUGAL IMPACT MILLING MACHINE Filed Sept. 12, 1955 6 Sheets-Sheet l rM/U 1 A i 'f I 56 "I- H v I 34 51, I i I I I INVENTOR. @fiuwfifiM/r 147 7' OP/YE V March 15, 1960 F. 5. SMITH 2,928,616

CENTRIFUGAL IMPACT MILLING MACHINE F-iled Sept. 12, 1955 6 Sheets-Sheet 2 INVENTOR.

L B 5 1 E ,wrqiz zv March .15, 1960 F. 5. SMITH 2,928,616

CENTRIFUGAL IMPACT MILLING MACHINE Filed Sept. 12, 1955 6 Sheets-Sheet 3 ATTOQNEV March 15, 1960 F. s. SMITH CENTRIFUGAL IMPACT MILLING MACHINE 6 Sheets-Sheet 4 Filed Sept. 12, 1955 IN V EN TOR. j/Zi/Nj jM/m BY 4 1M.

March 15, 1960 F. s. SMITH 2,928,615

CENTRIFUGAL IMPACT MILLING MACHINE Filed Sept. 12, 1955 6 Sheets-Sheet 5 mus? will.

IN V EN TOR.

March 15, 1960 F. 5. SMITH CENTRIFUGAL IMPACT MILLING MACHINE 6 Sheets-Sheet 6 Filed Sept. 12, 1955 milling machine structure.

Unite States 2,928,616 Patented. Mar, 15, 1960 ice CENTRIFUGAL IMPACT MILLING MACHINE Franklin S. Smith, Belieair Beach, Fla; The First National Bank of Clcaxwater, Clearwater, Fla, executor of said Franklin S. Smith, deceased, assignor to Manda R. Smith, Belleair Shore, Indian Rocks Beach, Fla.

Application September 12, 1955, Serial No. 533,702-

14 Claims. (Cl. 241-275) This invention relates to a centrifugal impact milling machine and more particularly to such a machine for effecting disintegration by imparting centrifugal velocity to the particles of a material to be reduced such as a food stock and by causing such particles to strike counter revolving targets at optimum impact angleand particle velocit'y. The present invention is characterized by high efficiency, increased life of the parts receiving the severest wear, and ease of maintenance and cleaning combined with compact construction. 7

Generally, particle milling machines having higher impact velocities accomplish more complete disintegration of the material undergoing treatment. Thus,'higher impact velocities, when practicable, are probably the most important single factor contributing to the effectiveness andefiiciency of the impact milling operation.

Since the impact velocity is a function of the diameter of the rotor imparting velocity to the particles, the kinetic force acquired by the particles from a constant speed. rotor may be increased by enlarging the size of the rotor, thus increasing its peripheral speed. Particles trajected in a general tangential direction from a larger rotor therefore have greater velocities and upon impact with the target array, efiect more complete disintegration of the material being milled. I 7

There are however limitations to the size of rotor which is practical to use in commercial centrifugal impact milling machines. Additionally, the optimum velocity of the particles being milled depends upon the material to be disintegrated and its condition.

For example, the first break of wheat in a grain milling operation may require only an impact velocity of the order of one hundred feet per second, whereas'each succeeding reduction requires a higher velocity up to and possibly beyond the order of four hundred feet per second.

7 To attain a particle impact velocity of the order of four hundred feet per second, a single rotor with stationary target would have to be 28 in diameter, if driven at 58 revolutions/second by a 60 cycle polyphase induction'motor. A single rotor impactor driven by a cycle, twopole motor at 24 revolutions/second would require a rotor 64" in diameter to produce a particle impact velocity of approximately 400 feet/second. V

Particle impact velocity may also be increased by increasing the rotor speed but'this expedient has serious attendant disadvantages when carried beyond certain limits. For instance significantly increased rotor speed sub jects moving contact parts, such as shafts and bearings, to markedly increased wear; increased rotor speed is more likely to cause troublesome air currents and eddies adja cent the target areas, thus interfering with optimum 'impact angle as Well as maximum impact velocity; and'the higher rotor speeds give rise, of course, to disproportionate stresses and strains'in the rotor itself and the entire Additionally, it may be mentioned that slower rotational speeds have theattractiveadvantage ofbeing much less likely to cause serious damage and wear tothe machine in the'event' of a structural rotor failure.

Moreover, the matter of target wear is always aproblem in impact milling machines and higher rotor speeds aggravate that problem. Even a relatively smallimprovement in extending the useful life of targets can be of significant valueand the manner in which the present invention overcomes this problem will be fully disclosed hereinafter. l

The prime object of the present invention is to provide a machine to disintegrate and divide material with improved efficiency both as to the effectiveness of the disintegration and increased product flow, without unnecessary increase in size or complexity of the apparatus. Another object oft he present invention is to provide a machine of the above character which increases the life of the target components used in the apparatus. Another object of the present invention is to provide a machine of the above character which increases milling machine efficiency and decreases power consumption. Another. object of the present invention. is to devise a machine of the above character having features which lend themselves to sound structural design for long, trouble-free life and easy maintenance. Another object of the present invention is to provide a machine of the above character which facilitates collisionof stock particles with the target surfaces at optimum impact velocities. Another object of the present invention is to provide a'machine of the above characterin which there is a minimum at- 'trition of stock. before, during and after impact. An-

other object of the present invention is to provide-a ma-' chine of the above character in which energy used in deforming and rupturing the stock is reduced to aminimum; Anotherobject of the present invention is'to provideta machine of the above character where heat generation due primarily to Work performed on the product" is reduced to a minimum. Another object of this invention is to provide a machine of the above character wherein the structure provides for a minimum of collisions between the particles being treated. Still another object of this invention is to provide a machine of the above character where air current eddies in the treatment zone between rotor and target array are greatly inhibited. Another object of this'invention is to provide a machine of the above character wherein power consumption is reduced to a minimum. Other objects will be in part. obvious and in part pointed out hereinafter.

The inventionaccordingly comprises a number of advantageous'aspects and features which. will be better understood by reference to the following detailed description of a preferred embodiment and the accompanying draw-. ings, in which:

Figure 3 is a vertical sectional view of the lower portion 7 of the" machine shownin Figure 1 with the upper or product' propelling distributing rotor raised for cleaning, repair or'inspection, as will be described,

Figure 4 is a horizontal sectional view taken along line,

4-4 of Figure 3,

' Figure 5 is a'horizontal sectional view taken along line 5-5'of Figure 2, 7

Figure 6 is a horizontal sectional view taken along line 66'of Figure 3, Figure 7 is a horizontal sectional view taken along the a line 7--7of Figure 3,

Figure 8 is a horizontal sectional view taken along the line 8-8 of Figure 3, V 1

gigure 9 is an enlarged top view of one of the targets, an a Figure 10 is an enlarged elevation, partially fragmentary and partially broken away, of a target mounted upon the target rotor.

Similar reference characters refer to similar parts throughout the several views of the drawings.

Asbest seen in Figure 1, the machine includes feed chutes generally indicated at 10 for gravity feeding a product such as grain or the like to the rotor casing g'enverally indicated at 12, the lower portion of which has depending sockets generally indicated at 14 for the legs 16 of the machine. As seen in Figures 1 and 2, a motor generally indicated at 18. is mounted above rotor casing 12 on an upper support generally indicated at 20. Motor 18 has a depending shaft generally: indicated at 22 (Figure 2) with a product propelling and distributing rotor generally indicated at 24 secured to the lower end thereof by a nut 25 threaded thereon. A lower motor generally indicated at 26 (Figure 3) is suspended from the bottom of casing 12 and has a shaft generally indicated at 28 extending upwardly therefrom and connected to a target rotor generally indicated at 30 by a conventional tapered shaft washer and a nut 31. As best seen in Figure 2; product propelling and distributing rotor 24 and target rotor 30 are disposed concentrically immediately beneath a split funnel generally indicated at 32 (Figure 2) connected to the chutes 10 in a manner to be described hereinafter. Thus the product to be treated is fed downwardly through chutes 10 into funnel 32 to be deposited on the distributing rotor 24. After treatment, by passage through the distributing and target rotors in a manner to be presently described; the product swirls and drops downwardly through the casing 12 and through a casing generally indicated at 34 to an outlet generally indicated at 36. j

Distributing rotor 24 includes a bottom plate 41 with Y a. substantially frustro-conical central portion 38' immeydiately beneath the bottom of funnel 32 and a pair of mounted within and secured to a shell 58 in a manner distributing rotor 24 as will be described. in greater dei tail hereinafter. Motors 18 and 26 may be of a suitable type capable of driving rotors 24 and 30 in opposite directions at desired speed to achieve desired work. on the product being treated. Accordingly, in operation; as the grain feeds down through chutes 10 and fnnnel32 it spreads outwardly illnstratively in two even streams between the plates 40, 41 and 42. Thus the centrifugal force exerted by theproduct shoots it out generally -tangentially from the periphery of the distributing rotor in two substantiallyvertically disposed streams so that the 6 individual particles hit the planar surfaces of the targets 46 thus achieving maximum impact with minimum attrition in a manner to be presently described. The product thence swirls'and drops downwardly and out of the machine through the outlet'hopper 36. 1

Turning now to Figure 3, sockets 14 are preferably integral with a lower ring portion 47 which is preferably frustro-conical in shape with an annular. shoulder 47a formed adjacent its lower edge. Casing 34 has an annu lar flange 48 on its upper edge shaped to interfit with shoulder 47a and these parts may be connected inany suitable manner as by screws (not shown); outlet 36 is connected to the bottom edge of casing 34 by screws 50. A pair of tubular members 52 and 54 (Figure 3) extend which has a depending annular flange 561;, ,Motor 26 is including cylindrical casing 78 wardly bell-shaped annulus to be described in detail hereinafter. As better seen in Figure 4,'tubular parts 64 aid 66 are preferably welded to casing 34 and extend inwardly therefrom and at right angles to tubular members 52 and 54. Cylindrical shell 58 is welded or otherwise secured to tubular parts 64 and 66 which thus support it and motor 26mounted therein; the upper' edge of shell 58 is secured to an annular angle ring 60 in turn connected to flange 56a by screws 62. Accordingly, the whole assembly including shell 58 and motor 26 is supported and held in position by tubular parts 62 and 64 which also function as air outlets'in a manner to be described; tubular members 52 and 54 merely act to hold the upper portion of the assembly in proper axial position. As can be understood from an extending sections 72 preferably integral therewith and connected to chutes 10 by screws 74. Converging passages 76 are formed in sections 72 thus connecting chutes 10 with the upper or top portion offunnel 32. Extending upwardly from sections 72 and connected thereto is a cylindrical casing 78 which is preferably integral with plates 80 extending between sections 72. Thus there isrpr'ovided a casing structure for the upper motor 18 l and a lower conoidal portion generally indicated at 81 which is roughly frustro conical in shape and includes sections 72 and plates 80 all shaped and positioned to support and enclose the motor 18; Ribs 82, preferably three in number, extend nfrom-cylindrical casing 78 and the motor casing generally indicated at 84 includes radially extending lugs 86 positioned above the ribs 82 and secured thereto by screws 88.

A bell-shaped annulus 90 having mtenorly extending reinforcing webs 90a and a flat annular top portion 906 base bottom flange 90c resting upon a similarly shaped and positioned flange 78a on the top edge ofcasing 78; screws 92 hold belles-haped annulus 90 to casing 78. .A cover plate 94 is secured to annulus 90 by screws 96 threaded into webs 9011 the parts being held in spaced relationship by. tubular spacers 97. Thus the top of casing12a'nd the enclosure for motor' 18 lnclpde top plate 68, sections 72, casing 78, connecting portions 80, 90 and cover plate 94 all for the protection of motor 18 while permitting cooling ventilation thereof in a manner to be described. As previously mentioned, motor casing 84 is secured to ribs 82 of casing 78 and the motor stator 98 of COIIVCH'. tional structure is securedwithin the casing in any well known manner." .Oil sealedbearings comprising a ball earing generallyindicated at 100 and a roller bearing generally indicated at 102 are connected to the top and bottom of motor. casing .84, as can be seen in Figure 2, and are of conventional construction with oil flingers 100a and 102a and feed pipes 104 and 106. Rotatively sup ported in bearings 100 and 102 in a well known manner is. a hollow motor shaft 108 conncctedto the rotor 110 108 and has formedon its upper section a plurality. of

' circumferentiallyspaced splines 112 formed thereon and interfitting with. correspondingly shaped. and positioned grooves 114 in hollow shaft 108. Thus shaft 22 rotates with hollowshaft 108 as a unit but may move axially with respect thereto for purpose to be presently described into casing 12 andare threaded into an annular part 56 Portions 116 and 118 of shafts 2 2 and 108 respectively v in positionby screws 158.

tire- 2 when-the distributing rotor 24-is in its lc'wermost position for an impactingqoperation'.

Whenit is desired to inspect, work on orremovethe distributing rotor 24 it may be raised to an upperposition as shown in Figure 3, for examination or passage through openings 87 and 89- in casing 12 (see also Figure 8). Thus, as shown in Figure 2, there is provided-a tripod generally indicated at 120 having legs 124 secured tocover plate 94 by screws 126. A stud shaft 128- is threaded in the top 130 of-tripod 120 and has formed on its lower end a thrust ball bearing head 132 fitting within an inverted cup-shaped member 134; suitable holes 22a and 132a are formed in the upper end of shaft 22 and cup134 so that a pin shown in dotted lines at 136 may beinserted as shown in Figure 2 to connect the cup member and shaft. Accordingly, it will beseen that when=desired distributing rotor may be raised by first removing split funnel 32. Then upon rotation of stud shaft 128 the axial position of shaft 22 with respect to hollow shaft 108 the rotor 24 may thus be raised to an upper position free and clear of the target rotor 30 and opposite openings 87 and 89. As can be seen in Figure 8, openings 87 and 89 are covered by separable flexible band closures 137 and 139 suitably secured to fixed pins 141 and 143 extending from casing 12 and tightened in position by tension bolt fasteners generally indicated at 145 and 147. Thus rotor 24 may be removed for repair or replacement. Upon lowering the shaft 22 to return .the distributing rotor 24 to its operating position tapered portions 116 and 118 of the respectiveshafts interfit. Accordingly shaft 22 will be supported Within shaft 108 and upon removal of .pin 136 it will rotate-therewith and the machine is ready to operate.

To cool motor 18 which is. completely enclosed in casing 78 and associated parts, a fan member 138 is screw threaded and keyed to hollow shaft 108 to rotate therewith immediately beneath. cover plate 94 and adjacent the openings between the. tubular spacers 97.- Asbest seenin Figures-2 and 5 openings 140 are formed in the conoidal portion 81 and fan 138 is designed so thatduring. operation of motor 18 its rotation draws air in through openings 140 thence to pass upwardly between the motor and casing 78 to be finally discharged through the openings immediately beneath cover plate 94. Accordingly there is a'constant cooling air circulation past motor 18 whenever it is operating.

Returning nowto Figure 3, as previously'noted cylindrical shell 58 issuspended from head 56 and lower motor 26 is mounted thereina More particularly, as will best be understood from Figures 3 and 6, the outer casing generally indicated at 142 of motor 26 includes four radially extending ribs 144 resting against the interior of cylindrical shell 58 and secured thereto to support the motor by screws 146. As can be seen in Figures 3 and 7 motor 26 has a top end bell generally indicated at 148 including radially extending lugs 158 located immediately above ribs 144 and secured thereto by screws 152. End bell 148 also contains an upper motor roller bearing 154 of conventional construction for rotatively supporting motor shaft 28 to be lubricated in a manner to bepresently described and including a sealing top cover 156 secured Motor shaft 28 is rotatively supported'in the lower portion of casing 142 by another bearing. structure 160 which-a1so takes the thrust load via shaft shoulder 161 resting thereupon and which may be secured in position by screws 162. Shaft 28 carries a rotor 164 held on a reducedportion 28a thereof in any convenient manner as by nut member 166 and the motor stator 168 is mounted in motor frame 142 between shoulder 170 and an annular extension 172 of end bell 148.

A bell-shaped reservoir 174 is secured to the bottom or frame 142 as by screws 176 to complete the motor as sembly and a pipe178 extendsbetween shell 58 and casing. 34 to canrythemotorwiring .188: Because motor .26-is; interiorly mounted provision must be made for adequate cooling-thereofzand thorough lubricationwofethe bearings 154 and 160. Accordingly, a=fan memberi'182 of conventionalstructure issecured to the upper end of shaft 28 adjacent tubular member 52 and within annular head 56; a cover plate 184 closes the'topof .the head and is secured thereto by screws 186. A bottom cover plate 187 is secured to the lower end of casingi58by bolts 188 threaded into a ring-190 which may be conveniently welded to the interior'of casing 58.

It will now be apparent that motor 26 is completely enclosed in casing 58 with bottom cover 187, head 56 and cover plate 184 completing the enclosure. enclosed space is connected with the outside-by cylindrical parts 64 and 66 (Figure 4) and via tubular members 52 and 54 at the top. .Accordingly, when themotor is operating fan member 182operates to suck air in through tubular members 64 and 66; thenceit passes upwardly around motor casing 142 and' between ribs 144 into head 56. It then passes out through. tubular members 52 and 54. In this manner, motor 26 is efiiciently cooled at all times during operation.

To properly lubricate bearings 1'54 and there-is an axial passage 192 formed in shaft 28 extending from the lower end thereof and connected to a radiallyextending passage 194 opening into upper bearing 154. A reservoir 196 is formed in end bell 148 immediately, beneath bearing 154 and is connected with lower bearing 160 by passage 198 in the end bell connected withua passage 200 in one of the ribs 144 byway of a quill 292. Reservoir 174 is connected to afilling and draining pipe 204 on the exterior of casing. 34 byqwayxof a tube 296.

after which it drains downzover upper bearings 154: and falls into reservoir 1%. From here it falls by gravity down through passage 198, quill 2G2 and passage-200 to lower bearing 1'60 and repeat the cycle.

Referring now to Figure 2, central opening-fila of plate 40 on distributing rotor 24 is slightly larger than the lower end 288 of funnel 32. Thus end 208 extends into the rotor to deposit all of the product entering the machine by way of the chutes 16 on central portion 38. The central opening 42a of plate 42 is smaller than opening 49a and is of such dimension as to provide an annular space between plate 42 and central portion 38 just back into reservoir 17410 large enough to divide the fiowingproductdnto two isubstantially equal streams, one flowing outupon plate 42 and one flowing out on the bottom plate 41 of the rotor. Thus the centrifugal force exerted by the productimpe-ls its passage, radially, in a manner to be described in greater detail presently.

.As better seen in Figure 8 Spacers 44 are substan tially tear shaped in cross section and the distributing clockwise direction as viewed from above. Targets 46 are mounted on bottom plate 212 of targetrotorblleo that their leading faces 46a are substantially radial-although they may be inclined forwardly with respect 'to the direction of rotation afew degrees. As best'seen Figure 10, tang 214, integral with target 46,1extend through tang holes. 226 of bottom plate-2 12 and are held in'such position by cap'nuts 216th-readed' thereon with washer 218 andlock-washer218izi Hills de;

This I In operation reservoir 174 is substantially full ofoil and thecentrifugal action of radialpas-sage 194 draws oil upwardly. through the axial passage'192 asses-is which isconc'entric with distributing rotor 24. These "targets may be mounted on plate 212 of the target rotor in any convenient'manner but preferably as illustrated i in Figures '9 and -10. The base of each target has three socket holes 22 2 on a circle concentric with tang 214 V and at intersections of radii to theapices of the target. A dowel pin 2% for each target is fixedly secured to andvextends upwardly from the upper face of bottomplate 212 of target rotor 30 and is '50 positioned that when inserted within one socket hole 222 it fixes and retains the target with its leading face in desired loca- *tion; Illustratively dowel pin 226 is inserted in the socket hole to the right as shown in Figures 9 and 10.

These targets are subject to considerable wear and particularly the leading surface 46a. However, it will be apparent from Figures 9 and 10 that any one of the target verticalsurfaces may become a leading 's'urface 46a by simply removing cap nut 216 and washers, lifting the target and rotating it until the dowel pin 226 fits within another socket hole in the base of the target; the washers are then replaced and the target is pulled into clamped position by the cap nut.

In operation both motors operate at high speed to rotate the distributing rotor 24 and the target rotor 30 in opposite directions. The product is fed down through the chutes and onto the outwardly and downwardly sloping surface of the central portion 38 of the distributing rotor to be divided into illustratively two even streams which are propelled in curvilinear paths outwardly on rotor 24. The individual particles of the stock rapidly pick up speed and as they reach the periphery of rotor 24 they are traveling at relatively high velocity and in general tangential directions as indicated by the arrows. Target rotor 30 on the other hand is being rotated at a high rate of speed in a clockwise direction and the leading'surfaces 46a ofthe targets 46 being substantially radial they are substantially normal to the tangential direction of travel of the particles; Consequently an impact of great magnitude is achieved between each particle of the stock and the target after which all the stock passes between the targets, travels on through and drops downwardly through the annular head 56', the ring 45 and into the annular passageway 228. From thence it leaves the machine via outlet 36.

The great majority of particles of stock collide with the leading surfaces 46a of the target at optimum velocity and thence pass immediately therethrough and down through the machine as described. Some of the particles may miss a direct encounter with one target, but in any event will slide along an inner face of the target and be thereby directed to the next leading target face 46a, collide with the next and in practice it has been found that collision between individual particles is reduced thereby avoiding this cushioning effect The construction ofthe distributing and target rotors is such as to minimize air current eddies in the treatment zone thereby materially increasing the efliciency of the impacting operation for there is nothing to impair the flight of the particles from the edge of the distributing rotor to the leading surfaces of the targets 46. Further,

still by the provision of these counter rotating rotors the size of all parts is greatly reduced which materially increases efiicicncy and reduces power consumption. Finally because maximum efliciency has been maintained in a relatively small machine the original cost of manufacture is materially reduced. V t

It will thus be seen that I have provided a thoroughly practical and eflicient centrifugal impact milling machine in which the several objects hereinabove referred to, as well as many others, have been successfully accomplished.

' Since certain changes may be made in the above construction without. departing from the. scope of the insaid rotor, an impact rotor rotatably mounted in axial alignment with said disturbing rotorincluding a bottom plate disposed beneath said product propelling rotor and of greater diameter than said product propelling rotor and a plurality of triangular impact targets equally spaced from each other and extending from said bottom plate on a circle, a first face of each of said targets facing the direction of travel thereof and being oriented substantially radial'to said rotors, the other faces being trailing faces and adapted thereby to guide particles impinging thereon toward the leading face of the next following target, said casing being radially spaced from said rotor and said circle being radially spaced from the periphery of said product propelling rotor so that said impact targets are concentric with said product propelling rotor, and means for driving said rotors in opposite directions whereby said particles are generally tangentially projected by said product propelling rotor, shattered by their impact with said impact targets and all of the shattered particles then pass between said impact targets and drop down through said casing by gravity.

2. The combination defined in claim'l in which the impact targets have the shape of an equilateral triangle in cross section. q

3. In a centrifugal milling machine for disintegration by impact of the individual particles of a granular stock such as grain, the combination of a casing, a product propelling rotor rotatably mounted therein, a motor mounted on top of said casing with its shaft connected to said rotor for driving said rotor, means forming chutes for guiding the stock to be milled by gravity inwardly betweensaid motor and said rotor to direct said stock to the central hub portion of said rotor, an impact rotor rotatably mounted in axial alignment with said distributing, rotor, means forming a frame fixedly positioned in a lower portion of said casing, a motor suspended from said frame and having its shaft connected to said impact rotor to drive the same, said impact rotor having a greater diameter than said product propelling rotor and said casing being radially spaced from said rotors, and a plurality of target impacteg extending upwardly from said impact rotor and radially spaced from the peripheryof said product propelling rotor whereby said impacters are concentric therewith so that particles of the stock are tangentially projected by said distributing rotor and shattered by their impact with said'target, all of said product passing between said target impacters to drop down to said casing.

4. In a centrifugal milling machine for disintegration by impactof the individual particles of a granular stock a bottom plate secured to a driving shaft; a plurality of impact'targets connected tosaid base and extending t upwardly therefrom, said targets being substantially on a circle and equally spaced circumferentially from each other; a product propelling rotor rotatably mounted in said casing and including a bottom plate and an annular top plate axially spaced therefrom both of said plates being connected to a second driving shaft, the diameter of said product propelling rotor being smaller than the diametric distance between said impact targets to provide an annular space between the periphery of said product propelling rotor and targets; duct means associated with said casing and terminating immediately above said product propelling rotor to direct the product to the central portion of said rotor between said bottom plate and said top plate; means for driving said shafts in opposite directions including a motor supported on the top of said casing to drive said product propelling rotor, and a motor enclosed within said casing below said rotors to drive said impact rotor; and means forming a passage through said casing and around said last mentioned motor whereby in operation the particles of the product are tangentially projected by said distributing rotor, shattered by their impact with the impact target, pass between said impact targets and fall down by gravity through said casing and around said last mentioned motor to leave the machine after treatment.

5. In a centrifugal milling machine for disintegration by impact of the individual particles of a granular stock such as grain, the combination defined in claim 4 in which the upper motor has a hollow shaft, a shaft slidably mounted within said hollow shaft and keyed thereto with its lower end connected to said product propelling rotor, and means for moving said last mentioned shaft axially with respect to saidhollow shaft.

6. In a centrifugal milling machine for disintegration by impact of the individual particles of a granular stock such as grain, the combination of a product propelling rotor including a base plate and an annular top plate spaced therefrom; an impact rotor rotatably mounted in axial alignment with said product propelling rotor and having a larger diameter than said product propelling rotor including impact targets disposed substantially on a circle and equally spaced thereabout and extending vertically from the bottom thereof, said impact targets being radially spaced from the periphery of said product propelling rotor, and means for driving said rotors in opposite directions, said targets being substantially triangular in cross section, each of said targets having a leading surface substantially facing the direction of travel thereof and two trailing surfaces angled from said leading surftce, whereby particles striking said leading surface may be disintegrated by impact thereon and particles impinging on said trailing surfaces may be guided toward the leading surface of the next succeeding target.

7. The combination defined in claim 6 in which said impact targets are substantially equilaterally triangular in cross section.

8. In a centrifugal milling machine for disintegration by impact of the individual particles of a granular stock such as grain, the combination of a casing, a product propelling rotor fixed to a shaft, a motor having a drive shaft, means interconnecting said shafts, one of said shafts being axially movable relative to the other, an impact rotor rotatably mounted in axial alignment with said product-propelling rotor and including a bottom plate disposed beneath said product-propelling rotor and of greater diameter, a plurality of impact targets equally spaced about said bottom plate in a circle radially spaced from the periphery of said product-propelling rotor, and means for axially moving said first mentioned shaft to move said product-propelling rotor away said impact rotor.

9. The combination defined in claim 8 in which there is an opening in said casing located above the operating position of said rotors and opposite the position said product-propelling rotor occupies when raised whereby the rotors may be conveniently serviced.

10. The combination defined in claim 8 in which said shafts are concentric and slidably keyed to each other.

11. The combination defined in claim 10 in which a threaded shaft is rotatably connected to the first mentioned shaft, said threaded shaft being threaded to a extension of said casing.

12. In a centrifugal milling machine for disintegration into said casing, a product-propelling rotor secured to said drive shaft, means permitting said drive shaft to move axially of but not radially of said mounting means, and means for feeding an article to be disintegrated to said product-propelliing rotor, whereby said rotor may be moved axially with respect to its operating position to permit access thereto for repairs and the like.

13. The combination defined in claim 12 including a second rotor having a plurality of targets concentric with and radially spaced from said product-propelling rotor, and means for driving said target rotor in a direction opposite to that of said product-propelling rotor, whereby particles may be accelerated by said product-propelling rotor against said targets to be disintegrated thereby.

14. In a centrifugal milling machine for disintegration by impact of the individual particles of a granular stock such as grain, the combination of a casing, a product propelling rotor rotatably mounted therein-and including an annular base plate, means for feeding a granular 7 stock to the central portion of said annular plate of said rotor, an impact rotor rotatably mounted in axial alignment with said distributing rotor including a bottom plate disposed beneath said product propelling rotor and of greater diameter than said product propelling rotor and a plurality of impact targets equally spaced from each other and extending from said bottom plate on a circle, said casing being radially spaced from said rotor and said circle being radially spaced from the periphery of said product propelling rotor so that said impact targets are concentric with said product propelling rotor, and means for driving said rotors in opposite directions whereby said particles are tangentially projected by said product propelling rotor, shattered by their impact with said impact targets and all of the shattered particles then pass between said impact targets and drop down through said casingby gravity, said casing having openings therein axially spaced from the operating position of said rotors, and means for moving one of said rotors axially with respect to the other to a position adjacent said openings.

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